Alternative Hydroponic Substrates-Rockwool/Stonewool Cube Product

Cultivating plants without soil, the accepted definition of hydroponics, continues to gain popularity within commercial horticulture, and as it does, more and more products are developed for it. More sophisticated lighting, easier to mix nutrients and simplified plant supports have all come onto the market within the past five years. But one of the most exciting developments in the world of hydroponics has been the refinement and popularization of alternative growing media.

There are probably hundreds of different kinds of growing media; basically, anything that a plant can grow in is considered a growing medium. Among the aggregates now available are rockwool/stonewool (the industry standard), oasis cubes, vermiculite, perlite, coconut fiber (coir), peat, composted bark, pea gravel, sand, expanded clay, lava rock, fiberglass insulation, sawdust, pumice, foam chips, polyurethane grow slabs and rice hulls. Each alternative has positives and negatives, and the choice between aggregates will depend on many variables, including the size and type of plants you wish to grow and the type of hydroponic system being used.

Rockwool/stonewool. Made from rock that has been melted and spun into fibrous cubes and growing slabs, rockwool has the texture of insulation and provides roots with a good balance of water and oxygen. Rockwool can be used with continuous drip or ebb and flow systems and is suitable for plants of all sizes, from seeds and cuttings to large plants.

Rockwool is considered by many commercial growers to be the ideal substrate for hydroponic production. Because of its unique structure, rockwool can hold water and retain sufficient air space (at least 18 percent) to promote optimum root growth. Since rockwool exhibits a slow, steady drainage profile, the crop can be manipulated more precisely between vegetative and generative growth without fear of drastic changes in EC or pH.

Note that some rockwool products require an overnight water soak before usage, as the bonding agents used to form slabs can result in high pH. Additionally, there has been a growing concern about disposing rockwool after use because it never truly decomposes.